1. Field of the Invention
This invention relates to a nonlinear optical waveguide device which uses .beta.-BaB.sub.2 O.sub.4 thin film on an .alpha.-Ba.sub.1-x Sr.sub.x B.sub.2 O.sub.4 substrate.
2. Description of the Prior Art
.beta.-BaB.sub.2 O.sub.4 has a relatively high nonlinear optical coefficient and is transparent up to the ultraviolet region, which is superior as a crystal for harmonic generation. In the past, however, it was only used as a bulk single crystal. Used in this way, the input power to the device was increased making it possible to increase the optical energy density.
For nonlinear optical devices which used .beta.-BaB.sub.2 O.sub.4 being transparent up to the ultraviolet region, an optical waveguide was necessary in order to increase the optical energy density without increasing the input power to the device.